The present invention relates to a composite concrete and metal building panel and a method for making the same. More particularly, the present invention relates to an improved composite panel having a metal stud frame structure with a molded concrete panel in which the metal stud frame is partially embedded in the concrete.
Composite concrete and steel frame panels have been used to construct floors, walls and ceilings in buildings, and as cladding panels in high-rise structures. It is well known to assemble composite building panels at one location and to transport the product to a construction site for use in fabricating structures. The use of prefabricated building components substantially reduces the labor costs at both the manufacturing and assembly processes.
Wood frames are commonly used in the building industry. Wood has the disadvantages of being susceptible to rotting and termite damage, and in addition, is highly flammable. For these reasons, wood typically has a lower potential life-span than other building materials.
On the other hand, concrete has a relatively longer life-span. Suited for very high compressive load bearing applications, concrete is a readily available building material. However, since concrete has a relatively low tensile strength, it is necessary to use metal reinforcement to improve the tensile strength of the panel if the panel is intended to carry load.
Composite panels made of concrete and metal frames are well known for providing exterior wall systems for commercial and industrial buildings, high-rise office buildings, and other applications. In most cases, the panels are supported on the building structure, and are not intended to bear any loading other than wind loading, however composite panels can also be used in load bearing applications. Generally, the panel includes a finished concrete surface forming the exterior of the building, and an interior surface for installation of insulation and finishings for the interior of the building. Structural steel studs, such as C-shaped channels, are assembled into a frame and the frame is partially embedded into a concrete slab. Embedding the frame into the concrete is typically accomplished by pushing the frame into the poured concrete and vibrating the concrete, or by attaching the frame to a jig or to conventional forms such that the frame is held supported a distance above the pouring pad. In the latter method, the concrete is poured and the jig or the forms are removed when the concrete is cured. A reinforcing layer, such as reinforcing mesh, is usually embedded in the concrete adjacent the channel to provide additional support to the frame.
U.S. Pat. No. 3,484,999 to C. Van Der Lely discloses a reinforced concrete slab for a wall, floor or roof. A frame of C-channel beams is located at the periphery of the slab, with the channels being partially embedded in the slab. A plurality of ribs are also partially embedded in the slab and are connected to a reinforcing member in the slab and to the peripheral frame. The panel is fabricated by placing the frame assembly on a jig and casting the concrete on a vibrating table to obtain a compact structure. When the concrete is cured, the panel is removed from the jig.
Staresina et al. disclose a composite building panel having a C-channel stud framework and a slab of cementious fiber reinforced material in U.S. Pat. No. 4,930,278. A flange of the C-channel abuts the surface of the slab such that a plurality of L-shaped tabs formed in the flange protrude into the slab. The panel is manufactured by pushing the frame down into the freshly poured concrete.
U.S. Pat. No. 5,526,629 to Cavaness discloses a composite building panel having a frame assembly around the perimeter of the panel and metal studs arranged within the bounds of the frame assembly. Having a general C-channel shape, one flange of the channels is embedded in a concrete slab. While the front of the panel is defined by the planar surface of the concrete slab, the back of the panel has the remaining portion of the C-channels protruding from the concrete. The remaining portions of the C-channels are used to join one panel to the next panel during installation on a building.
The Cavaness panel is manufactured by placing the assembled frame on a pouring pad and attaching form members (for example, wooden boards) around the perimeter. Concrete is poured from the rear of the panel until the concrete reaches a depth which embeds the flange. When the concrete is cured, the forms are disassembled.
Among the disadvantages of these composite panels, as well as other composite panels, is that the concrete slab is heavy. Consequently, the panels have to be thin in order to make them a feasible building alternative.
A further disadvantage of metal reinforced composite panels is that a line of weakness is created when the reinforcement abuts the channel, or other structural member.
Another disadvantage of metal reinforcement in concrete panels is that the metal located at the inner surface of the concrete can be exposed to moisture, which can lead to rust and mold, which is undesirable and costly to remedy.
A further disadvantage of metal reinforcement in concrete panels is that the embedded metal can shear the concrete from inside of the panel, particularly if the metal is not sufficiently anchored in the panel, causing the panel to fail.
Another common disadvantage of the concrete panel is that they have poor thermal and acoustic insulation properties.
Accordingly, there is a need to provide an improved composite panel and method of making in which the panel may be prefabricated at the construction site or elsewhere and transported to the construction site.
Another need is for an improved composite panel and a method of making in which the panel is strong, lightweight, fire resistant, thermally insulating, seismically resistant, sound attenuating and resistant to dampness, mold and rust.
A further need is for an improved composite panel and method of making in which the panel affords designers considerable latitude in the design, placement, and appearance of the panel.
Yet another need is for an improved composite panel and method of making in which the method of manufacture is less labor intensive than conventional composite panels.